[TangoTrotFox]

This hypothesis made a lot of sense in the past. It was logical and mapped to the data reasonably well. But I'm not sure it does anymore. Part of the reason that I mentioned the developed world is that people earning < $10k are not pumping out children in some sort of attempt to create a family that can provide sustenance and a strong lineage. Far from it - in today's urban societies, children are often more of an indefinite burden than a future tool for wealth creation. Maybe even more clear is considering the sharp decline in the middle class fertility over the past decades. Again it's not like those born in e.g. the 70s were that much less likely to survive to coming of age driving their parents to have that many more children. And again, the urbanization problem was also present then as well in any case.